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Document unreachable!() custom panic message

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The `unreachable!` docs previously did not mention that there was a second
form, `unreachable!("message")` that could be used to specify a custom panic
message,

The docs now mention this in the same style as currently used for `unimplemented!`:
https://doc.rust-lang.org/core/macro.unimplemented.html#panics
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Ed Morley 2021-11-11 13:41:21 +00:00
parent 62efba8a05
commit b41b2e5a5c
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1 changed files with 5 additions and 2 deletions
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7
library/core/src/macros/mod.rs
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@ -554,7 +554,10 @@ macro_rules! writeln {
///
/// # Panics
///
/// This will always [`panic!`].
/// This will always [`panic!`] because `unreachable!` is just a shorthand for `panic!` with a
/// fixed, specific message.
///
/// Like `panic!`, this macro has a second form for displaying custom values.
///
/// # Examples
///
@ -581,7 +584,7 @@ macro_rules! writeln {
/// if 3*i < i { panic!("u32 overflow"); }
/// if x < 3*i { return i-1; }
/// }
/// unreachable!();
/// unreachable!("The loop should always return");
/// }
/// ```
#[macro_export]